They may be tasty when you fry them up, but evidence is mounting that cephalopods like octopuses and squid possess consciousness. Over at the Cephalove blog, neuroscience student Mike Lisieski explains why.

The problem with measuring something like "consciousness" is that there is no agreed-upon definition. However, scientists can use a few basic tools to determine whether animals think in ways that humans would recognize as similar to themselves. You can measure (to a certain degree) whether a creature has self-awareness, independent problem-solving abilities, and exhibits brain activities that resemble "thinking" in the human brain.

In his essay, Lisieski walks us through three of these tests, and explains how cephalopods score.

Learning and object-recognition

First, do cephalopods exhibit self-awareness, which is to say are they aware of their environment and can they learn from it? Very few tests have been designed to suss this question out - partly because it's difficult to find a good cephalopod equivalent to the tests we do on rats, where the rodents learn to do tasks for a food reward. However, there were tests done on cephalopods in the 1970s where, as Lisieski puts it:

It was eventually concluded that octopuses (that is, individuals of the species O. vulgaris, the common octopus) don't use a set of simple rules to categorize objects. Rather, Mather argues, they "[evaluate] a figure on several dimensions and [generate] a simple concept, where [a] concept is an abstract or general idea inferred or derived from specific instances." Other evidence for the ability of cephalopods to exhibit learning like that taken to indicate cognitive ability (and thus the potential for consciousness) in vertebrate species comes from more complex learning tasks. The spatial learning abilities of cephalopods have been studied and it has been found, in general, that they might be capable of spatial learning to rival that of commonly used vertebrate laboratory species (such as rodents).

Tool use and adaptable behavior

What about the untrained behavior of cephalopods? This is another test: Does a creature exhibit consciousness-like behaviors when it is in the wild? The answer here seems more clear-cut. There are examples of cephalopods using tools in the wild, as you can see in this video taken of an octopus that carries around coconut shells to hide on the sea floor.

There is also evidence that octopuses change their behavior to suit different situations, such as opening different kinds of shelled animals differently - prying them open or drilling through the shell - depending on what gets them to the food inside most effectively. In one test, scientists wired shut a shell that the octopus would usually pry open. Finding that prying didn't work, it immediately switched to drilling. This kind of adaptive behavior suggests consciousness. These cephalopods weren't just following a hardwired algorithm in their brains. They were learning and changing their behaviors.

Brain behaviors

And finally, the most difficult thing to figure out: Do the brains of cephalopods exhibit patterns similar to those of conscious creatures like rodents or humans when measured with EEGs, for example? The problem here, as you can see from the diagram below, is that cephalopod brains are really different from mammal brains and even bird brains. We aren't sure what the structures of the cephalopod brain would correspond to in humans. However, Lisieski points out that cephalopods do seem to have "lateralized" brains, similar to humans and other primates, which allows for complex thought:

[Lateralization] seems to be one evolutionary result of the need for cortical tissue to be both locally differentiated and highly interconnected; it allows for more specialized cortical areas, because the right and left sides of the brain need not be functionally equivalent.

Electrical activity in cephalopod brains also changes as they tackle different tasks:

EEG-like recordings have been done in both octopus and cuttlefish, leading to the general (but very preliminary) finding that cephalopods have complex, low-frequency "background" electrical activity in some parts of their brains that seems to vary with their states of consciousness. In addition, they show sensory-evoked changes in this activity, in the same way that human EEGs do. This suggests that some of the gross functional properties of the cephalopod brain might resemble those of mammals on a system-wide level.

There's even evidence that cephalopods dream.

So are cephalopods conscious, or even intelligent? The jury is still out on that one. But I stopped eating cephalopods several years ago - even though they are very tasty - because I don't want a hyperintelligent cyberoctopus telling me one day that I ate her great-grandmother.

Read the rest of Lisieski's series on cephalopod consciousness via Cephalove